The present invention relates generally to plasma diagnostic instruments and more particularly to the use of a visible streak camera focused on open ends of optical fibers which transmit visible light pulses generated by various scintillators located in the region of plasma generation in response to emissions therefrom to investigate very rapid plasma formation.
In diagnosing subnanosecond, high energy laser-target or high energy particle beam-target interactions, the use of optical fibers presents two attractive features: (1) miniaturization of detectors permits improved flexibility in placing detectors at the most desirable locations and in greater number than can normally be accommodated; and (2) the detectors are insensitive to electromagnetic noise generated by the laser or particle beam produced plasmas as well as to the high-voltage components associated with the high-energy laser or particle beam system. However, in the vicinity of targets utilized in laser or particle beam fusion experiments, the great flux of X-ray radiation and intense emission of relativistic electrons and fast ions do present serious noise problems which severely limit the straight-forward employment of optical fibers in diagnostic instrumentation. Judicious selection of fiber material and the entrance aperture, proper choice of fiber orientation and shielding, and the use of spectral filter and relay optics, it is possible to overcome some of these difficulties and derive useful information. The extremely high recording speed of the visible streak camera when combined with the flexibility and versatility of optical fibers permits the very difficult subnanosecond laser or particle beam produced plasma diagnostics.
The following properties of streak cameras make such plasma diagnostics possible: 1. sub-100 ps recording speeds; 2. micron spatial resolution; and 3. high sensitivity because of image intensification. Photomultiplier tubes can achieve similar response times but the oscilloscopes required to record photomultiplier output are much slower. Moreover, phototubes have no spatial resolution so that only one fiber output can be detected and recorded by each photomultiplier tube. Ordinary cameras have no time resolution capability and are much less sensitive thereby making them of limited value for plasma diagnostics.